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Non-native and Invasive Plants in the
Lower Coos Watershed

    Summary:

  • Seven invasive plant species already established in the project area
    pose imminent environmental or socioeconomic threats; 10 species
    not yet present in the project area are expected to cause problems
    in the future.


  • European beachgrass (Ammophila arenaria) and gorse (Ulex
    europaeus) are two non-native invasive plant species that have
    significantly changed the local landscape. Beachgrass is well
    established in the project area and gorse is common to the south.




Locations of select non-native invasive plants established in the project area in isolated populations or species that are currently being targeted for removal or control actions.

Locations of select non-native invasive plants established in the project area in isolated populations or species that are currently being targeted for removal or control actions.

Meadow knapweed Photo: ODA

Meadow knapweed Photo: ODA

Gorse  Photo:  ODF 2014b

Gorse Photo: ODF 2014b

Threat icon graphic

Threat icon graphic


Color code graphic

Color code graphic

What’s happening?

The threat status of the non-native and
invasive vegetation species discussed in each
section is indicated by icons and colors. A
butterfly/slash icon indicates plant species
with high potential to cause environmental
harm; these species outcompete native flora
and alter natural ecosystems. The dollar sign
icon indicates plant species with high potential
to cause serious socio-economic harm
(see threat icon graphic). Threat levels are
indicated by color codes- red being the greatest
threat, pale yellow the lowest threat (see
color code graphic).

Each section also includes a summary table
listing the species discussed in the section
along with general information about their
introduction and impacts in Oregon. Species
are color-coded using the same icon color
codes described above- red being the greatest
threat, pale yellow the lowest threat (see color code graphic).

Table 1. Predicted non-native and invasive vegetation species threats. * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species: Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program. ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a).

Table 1. Predicted non-native and invasive vegetation species threats. * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species: Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program. ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a).

This data summary describes available data
for non-native and invasive (see sidebar) vegetation
species found locally and is divided,
like other data summaries, into two sections:
1) What’s happening?; and 2) Background.

The What’s happening? section focuses on
the presence, distribution, and threat levels
associated with priority non-native and
invasive plant species, and is divided into
three subsections: 1) Predicted Threats; 2)
Partially Contained Threats; and 3) Established
Threats. The subsections are defined as
follows:

1) Predicted threats – invasive vegetation
not yet found in the project area but will
be in the future.
2) Partially contained threats – invasive
vegetation currently found only in isolated
populations within the project area.
3) Established threats – invasive vegetation
found across much or all of the project area.

The Background section provides detailed
descriptions of the specific threats posed by
each of the 58 non-native and invasive plant
species included in this data summary.

Non-native species – Plants or animals
introduced either intentionally or accidentally
to locations outside their native
ranges.

Invasive Plant – Non-native plants or animals
that aggressively outcompete native
vegetation causing significant economic
loss and/or environmental harm. Not all
non-native species are invasive.

Noxious Weeds – Invasive plant species
listed at the county, state or federal level
as particularly harmful to public health,
wildlife, agricultural activities, or public
and private property.


Predicted Threats (Table 1)

These species have nearby established populations
(adjoining counties or states) and are
imminent threats to the project area. Several
species have been introduced in the past but
have since been eradicated.

Cordgrasses (Spartina spp.)

Three invasive cordgrass species are considered
serious potential economic and environmental
threats to the Coos estuary:

Smooth cordgrass (Spartina alterniflora),
considered the most aggressive of the invasive
cordgrass species, has been found once
in the Coos estuary at the Oregon Department
of Transportation’s (ODOT) Barview
Wayside wetland mitigation site near Barview
(Figure 1). This population was accidentally
transplanted during the wetland mitigation
re-vegetation work. Because they never
produced seed heads, the mysterious plants,
growing into two large clones in the middle
of the wetland, were very hard to positively
identify (Figure 2). What was later identified
using genetic techniques as smooth cordgrass
was manually removed from the site over
the course of seven years, both before and
after the plant was positive identified. Helped
immeasurably by the absence of seed production,
smooth cordgrass is now considered
completely eradicated at the Barview Wayside
site. Aside from a site in the Siuslaw estuary
(where the Barview Wayside infestation

Figure 1: Locations of historic cordgrass infestations in the Coos estuary. All known plants have since been eradicated. Data: SSNERR 2013

Figure 1: Locations of historic cordgrass infestations in the Coos
estuary. All known plants have since been eradicated. Data:
SSNERR 2013




Figure 2. Top left: Smooth cordgrass (Spartina alterniflora) clones (black arrows) at Barview Wayside in 1995. Top right: close-up of a flowering smooth cordgrass seed head which never developed at Barview Wayside. Middle left: Dense-flowered cordgrass (Spartina densiflora) in Coos Bay near Jordan Cove (2013). Middle right: Close-up of dense-flowered cordgrass flowering head. Bottom left: Saltmeadow cordgrass (Spartina patens). Bottom right: Common cordgrass (Spartina anglica).

Figure 2. Top left: Smooth cordgrass (Spartina alterniflora)
clones (black arrows) at Barview Wayside in 1995. Top
right: close-up of a flowering smooth cordgrass seed head
which never developed at Barview Wayside. Middle left:
Dense-flowered cordgrass (Spartina densiflora) in Coos
Bay near Jordan Cove (2013). Middle right: Close-up of
dense-flowered cordgrass flowering head. Bottom left: Saltmeadow
cordgrass (Spartina patens). Bottom right: Common
cordgrass (Spartina anglica).


Garlic mustard (Alliaria petiolata)

Although not known to occur in Coos County,
the Coos County Weed Advisory Board has
determined that garlic mustard can cause
harm to the local forest ecosystems by dominating
forest understory plant communities
(Coos Weed Board 2011)(Figure 3). The Oregon
Department of Agriculture (ODA) reports
that the nearest county known to have garlic
mustard is Josephine, just southeast of Coos
County (ODA 2014).

Figure 3. Thicket of garlic mustard (Alliaria petiolata) and close-up of flowers. Photos: ODA 2014a; EDDMapS 2014.

Figure 3. Thicket of garlic mustard
(Alliaria petiolata) and close-up of
flowers. Photos: ODA 2014a; EDDMapS
2014.


Portuguese Broom (Cytisus striatus)

Portuguese Broom infestations in Oregon are
only known in Lane and Douglas Counties,
with the closest documented location just
south of Florence (ODA 2014a)(Figure 4). In
North America, it only occurs in California
and Oregon (Zouhar 2005a). The Coos County
Weed Advisory Board has listed this species
as a species of high concern due to its detrimental
economic impacts and the likelihood
of this species to infest Coos County (Coos
Weed Board 2011). The California Invasive
Plant Council lists Portuguese broom as one
of the most invasive wildland pest plants in
regional areas of the state (Zouhar 2005a).

Figure 4. Portuguese Broom (Cytisus striatus) plant and close up of seed pods. Photos: ODA 2014a

Figure 4. Portuguese Broom
(Cytisus striatus) plant and close up of seed pods.
Photos: ODA 2014a


Giant Hogweed (Heracleum mantegazzianum)

Giant hogweed has yet to be found in the
project area, but has limited distribution
along the northern Oregon coast (ODA
2014a). Moist wooded riparian areas of the
project area would provide perfect habitat for
this species and allow it to reach its full
reproductive potential (Figure 6)(Forney 2013).







Partially Contained Threats (Table 2)

Species described in this section have become
established in the project area in isolated
pockets, and whose populations are either
being actively managed or were just recently discovered.

Old Man’s Beard (Clematis vitalba)

So far, old man’s beard has limited distribution
in the project area. It is, however, fairly
widespread along the South Fork Coos River
(Figures 8 and 9)(ODA 2014a; A. Brickner,
pers. comm. 2014). Old man’s beard is much
more common in northwestern Oregon and is
expected to become widespread throughout
most of the state due to this species’ highly
effective seed dispersal strategy (ODA 2014a).

False Brome (Brachypodium sylvaticum)

medium-high-env-threat-butterfly-icon

Identified in the South Slough watershed in
2006 by ODA, Oregon is considered the “epicenter
for false brome” in the U.S. (Figures 8
and 9)(EDDMapS 2014, ODA 2014a).

First discovered in North America (specifically,
in Eugene) in 1939, this perennial grass has been
naturalized (a self-sustaining population) in
the Corvallis/Albany area since at least 1966
and has now taken over an estimated 10,000
acres in Oregon (Chambers 1966; Davi 2009;
ODA 2014a).

Distribution of false brome is expected to
become more widespread since the species
has had time to genetically evolve and adapt
(Holmes et al. 2010).

originated), and a site at the mouth of the
Columbia River, the Barview Wayside infestation
is the only documented case of smooth
cordgrass becoming established in Oregon.

According to Howard et al. (2007), regional
invasions occur in San Francisco, CA, which
has a large (~1,000 acres in 2006) smooth cordgrass population,
and to the north, in Willapa Bay, WA where populations peaked in
2003 with 8,500 acres affected, costing Washington
state over $3 million from 2005-07.

Dense-flowered cordgrass (Spartina densiflora)
plants were found in the Coos estuary
in 2013 near Jordan Cove, the first time this
species has been found in Oregon (Figures 1
and 2). Five individual clones were found and
subsequently removed. According to Howard
et al. (2007), over 1,500 acres of marsh
habitat in Northern California have been
converted to dense flowered cordgrass-dominated
systems. For example, dense-flowered
cordgrass now occupies 94% of Humboldt
Bay’s remaining salt marsh habitat.

Saltmeadow cordgrass (Spartina patens)
is only known to occur in Oregon on Cox Island
in the Siuslaw River (Howard et al. 2007)(Figure
2). Present since the 1930’s, eradication
of this population began in 1996 and is still
ongoing. As of 2006, San Francisco (California)
had a small (< 1 acre) population of this species (Howard et al. 2007).

Common cordgrass (Spartina anglica)
has never been found in Oregon, but has established
populations in both the Puget Sound
to the north and San Francisco to the south
(Howard et al. 2007)(Figure 2).




Diffuse Knapweed (Centaurea diffusa)

Diffuse knapweed, which occurs in all surrounding
counties but not yet in Coos County,
is listed by the Coos County Weed Advisory
Board as a species expected to be extremely
damaging to the local economy if allowed to
take hold (Coos Weed Board 2011)(Figure 5).
This species cannot tolerate flooding or shading,
therefore it is most likely to be found in
drier pasture or cropland areas (Beck 2013).
Duncan (2001 as cited in Zouhar 2001a)
reports that Oregon had nearly one million
acres of diffuse knapweed infesting it in 2000.

Figure 5. Diffuse knapweed (Centaurea diffusa). Photos: Beck 2013; ODA 2014a

Figure 5. Diffuse
knapweed (Centaurea
diffusa).
Photos: Beck
2013; ODA 2014a


Herb Robert (Geranium robertianum)

Herb Robert is not known to occur in the project
area, but there has been positive identification
of this species in Coos County by the
United States Forest Service (USFS) in 2002
(Figure 7)(EDDMapS 2014). According to ODA
(2014a), Herb Robert has the potential to
become the most common woodland invader
in Western Oregon.

Figure 7. Herb Robert (Geranium robertianum). Photo: ODA 2014a

Figure 7. Herb Robert (Geranium robertianum).
Photo: ODA 2014a


Woolly Distaff Thistle (Carthamus lanatus)

Wooly distaff thistle is not known to occur in
Coos County, but it can be found in all surrounding
counties (ODA 2014a; OSU 2006).
According to Burrill (1994), Wooly distaff thistle
is a federally listed noxious weed considered
one of the worst pasture weeds in North
America and Australia.

Figure 6. Giant hogweed (Heracleum mantegazzianum). Photos: ODA 2014a

Figure 6. Giant
hogweed (Heracleum
mantegazzianum).
Photos:
ODA 2014a






Policeman’s Helmet (Impatiens glandulifera)

Until recently, infestations of policeman’s
helmet have been restricted to northwestern
Oregon. However, in 2014 this species was
found in the project area (Figures 8 and 9)
(ODA 2014a; A. Brickner, pers. comm. 2015).
Oregon invasions have come from expansion
of established populations in western
Washington and lower British Columbia (ODA
2014a).

Spanish Heath (Erica lusitanica)

Within the project area, Spanish heath occurs
along Cape Arago Highway (Figures 8 and 9)
(A. Brickner, pers. comm. 2015). First introduced
at a rare plant nursery near Langlois
OR, Spanish heath has become established in
seven Oregon locations, mainly in Coos and
Curry counties. It’s well adapted to the moist
acidic soils of coastal Oregon and is a prolific
seed-bearer. Spanish heath is expected to
spread exponentially in the coming years.
High costs associated with controlling established
populations make Spanish heath a high
priority for early eradication (French 2009).

Vectors of invasion


Not being aware of some plants’ aggressive
potential, people intentionally introduce
what turn out to be invasive terrestrial
vegetation to their local areas:
„„

  • As garden ornamentals (e.g., butterfly
    bush, Scotch broom, gorse)
  • „„

  • For agriculture land enhancements
    (e.g., false brome, reed canary grass)
  • „„

  • For use in aquariums or water features
    (e.g. Eurasian watermilfoil, Brazilian
    waterweed)
  • „„

  • For use as bank or dune stabilization
    (e.g., European beach grass)

  • Accidental invasive species introductions
    also occur, often the result of seeds or vegetative parts hitchiking on:
    „„

  • Internationally traded goods (e.g.,
    biddy-biddy in sheep’s wool)
  • „„

  • The boots or clothing of individuals
    traveling from infested regions
  • „„

  • Migrating animals

  • Animals can also spread non-native and invasive plants by ingesting seeds and
    dropping seed-laden feces in areas with hospitable growing conditions (e.g., cotoneaster, English ivy).


    Table 2. Partially contained non-native and invasive vegetation species threats. * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species: Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program. ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a).

    Table 2. Partially contained non-native and invasive vegetation species threats. * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species: Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program. ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a).

    Figure 8. Partially contained species. Clockwise from top: Policeman’s helmet (Impatiens glandulifera)(inset: flower); Yellow flag iris (Iris pseudacorus); Old man’s beard (Clematis vitalba)(inset: leaves and flower); Spanish heath (Erica lusitanica); Dalmatian toadflax (Linaria dalmatica). Middle: False brome grass (Brachypodium sylvaticum). Photos: ODA 2014a; Stone 2009; Lincoln county soil water conservation district; kingcounty.gov; wikipedia.

    Figure 8. Partially contained species. Clockwise from top: Policeman’s helmet (Impatiens glandulifera)(inset: flower); Yellow flag iris (Iris pseudacorus); Old man’s beard(Clematis vitalba)(inset: leaves and flower);Spanish heath (Erica lusitanica); Dalmatian toadflax (Linaria dalmatica). Middle: False brome grass (Brachypodium sylvaticum). Photos: ODA 2014a; Stone 2009; Lincoln county soil water conservation district; kingcounty.gov; wikipedia.

    Spurge Species (Euphorbia spp.)

    Approximately 12 spurge plants whose identification have not been finalized can be found at three locations in the project area. These
    spurge species are most likely leafy spurge (E.
    esula
    ) or oblong spurge (E. oblongata)(Figure
    9). The plants will be positively identified and
    pulled in the summer of 2015 (A. Brickner,
    pers. comm. 2015). Oblong spurge is only
    known to occur in three Oregon counties,
    Lane County being closest to the project
    area (ODA 2014a). Rare along coastal Pacific
    Northwest in 1994, leafy spurge is more common
    in eastern Oregon counties, but occurs
    in Curry County to the south (Pojar and MacKinnon
    1994; USDA 2015).

    Yellow Flag Iris (Iris pseudacorus)

    Yellow flag iris is an aquatic plant found sporadically within the project area and is more
    common further north (e.g., Umpqua River)
    (Figures 8 and 9)(A. Brickner, pers. comm.
    2015; ODA 2014a).


    Established Species (Table 3)

    The following list of priority, already established
    non-native and invasive plant species
    (listed in Table 3 which spans two pages), are
    found throughout the project area, either in
    widespread or limited populations.

    Beachgrass (Ammophila spp.)

    Two related invasive beachgrass species occur
    in Oregon: 1) European beachgrass (Ammophila
    arenaria
    )(native to Europe); and 2) American
    beachgrass (A. breviligulata)(native to the
    east coast of North America )(Figure 10). European
    beachgrass was introduced to Oregon
    in 1910 near Coos Bay for dune stabilization
    and now dominates the dune system (Crook
    1979). American beachgrass was intentionally
    planted near the mouth of the Columbia River
    in the 1930s and has since spread south.
    According to Hacker et al. (2012), American
    beachgrass was only found in isolated patches
    in Coos County, where the dunes are dominated
    by European beachgrass. Since their
    introduction in Oregon, beachgrasses have
    created a nearly continuous barrier from the
    foredunes inland to Highway 101, completely
    changing the formerly dynamic dune system
    (Crook 1979). Aerial photography of Oregon
    dunes from 1939 show 20% vegetative
    coverage; 50 years later over 80% of dunes in
    the same region were covered by vegetation
    (USFS n.d.).

    Figure 11. Known locations of gorse (Ulex europeaeus) infestations in the project area. Sources: ODF 2014a; EDDMapS 2015; CoosWA 2014a

    Figure 11. Known locations of gorse (Ulex europeaeus) infestations
    in the project area. Sources: ODF 2014a; EDDMapS
    2015; CoosWA 2014a


    Figure 12. Established species with limited distribution in the project area that have the greatest potential impacts to the project area (clockwise from top left): gorse (Ulex europaeus); Himalayan knotweed (Polygonum polystachyum); giant knotweed (Polygonum sachalinense); and Eurasian watermilfoil (Myriophyllum spicatum). Photos: ODA 2014a

    Figure 12. Established
    species with limited
    distribution in the project
    area that have the greatest
    potential impacts to the
    project area (clockwise from top left): gorse (Ulex europaeus);
    Himalayan knotweed (Polygonum polystachyum); giant
    knotweed (Polygonum sachalinense); and Eurasian watermilfoil
    (Myriophyllum spicatum). Photos: ODA 2014a

    Figure 9. Known locations of several weeds that are thought to be partially or fully contained. Source: A. Brickner pers. comm. 2015; EDDMapS 2014.

    Figure 9. Known locations of several weeds that are thought to be partially or fully contained. Source: A. Brickner pers. comm. 2015; EDDMapS 2014.

    Dalmatian Toadflax (Linaria dalmatica)

    Dalmatian toadflax was positively identified
    in Charleston in 2014 for the first time within
    the project area (Figures 8 and 9)(A. Brickner,
    pers. comm. 2015). Many Oregon counties
    east of the Cascades have widespread infestations
    of this species (ODA 2014a).



    Figure 10. Top: Oblique sand dunes before beachgrass (Ammophila spp.) invasion. Middle: Inspection of intentional plantings of beachgrass in the Oregon Dunes Recreation Area c1930’s. Dunes were planted to stabilize the highly mobile sand. Bottom: Bulldozer taking down a foredune north of Reedsport. The foredune was largely created by beachgrass (seen behind the bulldozer). Sources: University of Oregon Libraries; Siuslaw National Forest (bottom two photos); Coos Bay BLM (inset)

    Figure 10. Top: Oblique sand dunes before beachgrass (Ammophila spp.) invasion. Middle: Inspection of intentional plantings of beachgrass in the Oregon Dunes Recreation Area c1930’s. Dunes were planted to stabilize the highly mobile sand. Bottom: Bulldozer taking down a foredune north of Reedsport. The foredune was largely created by beachgrass (seen behind the bulldozer). Sources: University of Oregon Libraries; Siuslaw National Forest (bottom two photos); Coos Bay BLM (inset)



    Gorse (Ulex europaeus)

    So far, gorse is found only in relatively small,
    isolated patches around the Coos estuary
    (Figures 11 and 12)(SHN 2013; A. Brickner,pers. comm. 2015; OR Dept. of Forestry [ODF]
    2014a; CoosWA 2014a; EDDMapS 2014).
    Infestations at many of these locations are
    controlled by the Coos Watershed Association
    (CoosWA) and in some cases herbicide (Garlon
    3A or triclopyr)(A. Brickner, pers. comm.
    2015). Just south of the project area, gorse
    has completely overtaken native vegetation
    in many expansively infested landscapes.
    ODF conducted an aerial survey of 300,000
    acres in coastal Coos and Curry counties in
    the spring of 2014; they recorded over 6,200
    acres of gorse, nearly 4,400 acres of which
    were heavily infested (ODF 2014a).

    French broom (Genista monspessulana)

    Widespread on the southern Oregon coast,
    this plant prefers warm, moist, low elevation
    areas (ODA 2014a)(Figure 13). French broom
    is the most widespread broom in California
    (Zouhar 2005b).

     Table 3 (continued next page). Established non-native and invasive vegetation species threats.* Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species:Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program.** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a)*** Non-native species not considered to be invasive.

    Table 3 (continued next page). Established non-native and invasive vegetation species threats.
    * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species:
    Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program.
    ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a)
    *** Non-native species not considered to be invasive.

    Table 3 (continued from previous page). Established non-native and invasive vegetation species threats. * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species: Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program. ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a) *** Non-native species not considered to be invasive.

    Table 3 (continued from previous page). Established non-native and invasive vegetation species threats.
    * Listed species are considered noxious weeds by the state of Oregon (Oregon Department of Agriculture). A-listed species: Economically threatening weed which occurs in small enough infestations to make eradication or containment possible; or is not known to occur in the state, but its presence in neighboring states make future occurrence in Oregon imminent. B-listed species:
    Economically threatening weed which is regionally abundant, but may have limited distribution in some counties; T-listed species: Weeds annually selected from A or B listed species as the focus of prevention and control by Oregon’s Noxious Weed Control Program.
    ** Weed distribution color key: Yellow: limited; Red: widespread; Green: historical; Gray: not known to be present. (ODA 2014a)
    *** Non-native species not considered to be invasive.

    Figure 13. Established species with widespread distribution in the project area that pose the greatest threats to the project area. Top row: reed canary grass (Phalaris arundinacea); French broom (Genista monspessulana); Scotch broom (Cytisus scoparius); Middle row: Brazilian waterweed (Egeria densa); jubata grass (Cortaderia jubata); purple loosestrife (Lythrum salicaria). Photos: ODA 2014a; U of FL (Brazilian waterweed); and OSU (reed canary grass).

    Figure 13. Established species with widespread distribution in the project area that pose the greatest threats to the project area. Top row: reed canary grass (Phalaris arundinacea);French broom (Genista monspessulana); Scotch broom (Cytisus scoparius); Middle row: Brazilian waterweed (Egeria densa); jubata grass (Cortaderia jubata); purple loosestrife (Lythrum salicaria). Photos: ODA 2014a; U of FL (Brazilian waterweed); and OSU (reed canary grass).

    Knotweeds (Polygonum spp.)

    medium-high-env-threat-butterfly-icon

    There are four knotweeds known in the
    project area: Himalayan (P. polystachyum),
    Japanese (P. cuspidatum), giant (P. sachalinense),
    and Bohemian (P. bohemica)(a hybrid
    between giant and Japanese knotweeds)
    (Figure 12). Himalayan knotweed is the least
    common of the three non-hybridized species
    in the Pacific Northwest, while Japanese knotweed
    has the most widespread distribution,
    especially in western Oregon (ODA 2014a).
    CoosWA provides free herbicide application
    to knotweed infestations for any landowner
    within the Coos watershed. Because of this
    effort, between 2008 and 2012, knotweed infestation in the Coos watershed was reduced
    from 12 acres to three (Cornu et al. 2012).

    Purple loosestrife (Lythrum salicaria)

    medium-high-env-threat-butterfly-icon

    Found along moist sites in most subsystems
    of the project area, purple loosestrife populations
    are especially dense along Catching
    Slough and near the Libby area of Coalbank
    Slough (Figures 13 and 14)(CoosWA 2014b).

    Butterfly bush (Buddleja davidii, formerly B.
    variabilis)

    Out of all Oregon counties, butterfly bush is
    most widespread in Coos and Lane counties
    (ODA 2014a). In the project area, it’s been
    most frequently reported along Cape Arago
    Hwy, Isthmus Slough, and the mouth of the
    Coos River (EDDMapS 2015).

    Knapweed or starthistle (Centaurea spp.)

    There are three knapweed/starthistle species
    known to occur in the project area – spotted
    knapweed (C. stoebe, formerly C. maculosa),
    meadow knapweed (C. pratensis) and yellow
    starthistle (C. solstitialis). A fourth invasive species, diffuse knapweed, (C. diffusa) has
    not been found locally and is described under
    Predicted Threats above.

    Because yellow starthistle, already infesting
    nearly one million acres of Oregon rangeland
    (Duncan 2001 as cited in Zouhar 2002), prefers
    dry conditions with full sunlight, it’s not
    likely to heavily infest the project area. Meadow
    knapweed, on the other hand, favoring
    moist conditions (e.g. riverbanks or irrigated
    pastures), can become established in a wide
    range of local environments (ODA 2014a;
    OSU 2006; Zouhar 2002). Spotted knapweed
    tolerates both wet and dry conditions, but
    prefers areas that receive summer rainfall
    (Beck 2013; PCA 2005). According to Zouhar
    (2001b), nearly 800,000 acres of Oregon
    lands were infested with spotted knapweed
    in 2000.

    Japanese eelgrass (Zostera japonica)

    Japanese eelgrass coverage has not been
    quantified in the Coos estuary, but it commonly
    occupies previously unvegetated
    mudflat areas (Shafer et al. 2011). Japanese
    eelgrass was first observed in the Coos
    estuary in the mid-1970’s in South Slough.
    By the mid-1980’s it had spread throughout
    the South Slough and to middle portions of
    the Coos estuary (Posey 1988). This eelgrass
    invader has since increased its distribution
    and density in the Coos estuary (Rumrill
    2006). Japanese eelgrass grows on the Coos
    estuary’s mid-intertidal mudflats (0.6-1.2 m[2.0-4.0 ft] above mean lower low water) and
    generally does not compete with the native
    eelgrass (Z. marina), which grows on lower
    intertidal mudflats and in subtidal channels
    (Posey 1988). In Yaquina Bay, Japanese eelgrass
    coverage has increased by 400% in just
    over nine years (Young et al. 2008).

    Sweet Fennel (Foeniculum vulgare)

    Fennel is considered only moderately invasive.
    Expansive populations can be found in
    coastal southern Oregon (NPSO 2008).





    Beachgrasses (Ammophila spp.)
    Non-native European and American Beachgrasses
    are well adapted to seasonal sand
    burial (up to 1 m per year according to Ranwell
    1959 as cited in Russo et al. 1988), which
    allows them to outcompete the native dune
    grass, Elymus mollis (a.k.a. Leymus mollis).
    Invasive beachgrasses spread via rhizomes
    (i.e., rootstock), the fragments of which are
    dispersed along the shore by winter storms
    (Russo et al. 1988). Once established, these
    species are very difficult to control, much less
    eradicate.

    Since the introduction of beachgrasses to the
    Oregon dunes, populations of native plant
    and animal species adapted to once dynamic
    Oregon dune habitats (including pink sand
    verbena, wolf’s evening primrose, silvery
    phacelia, and the endangered western snowy
    plover), have declined precipitously (Figure
    10)(Julian 2012, Kaye 2004, Kalt 2008, Russo et al. 1988).

    Russo et al. (1988) attributed native dune
    species decline largely to changes in the
    orientation of the Oregon dune field’s valleys
    (technically referred to as “slacks”) and to
    the reduction in sand supply to interior dune
    habitats, both caused by the establishment of
    non-native beachgrasses. Historically, beaches
    associated with the Oregon dunes were characterized
    by the absence of foredune habitat
    running parallel to the ocean shore. Dunes
    and associated slacks were instead oriented
    obliquely to the shore, shifting with seasonal
    changes in prevailing winds. The Coos Bay
    dune field (stretching from Haceta Head in the north and Cape Arago in the south, the
    largest dune sheet in North America) contains
    the only “oblique-ridge dunes”’ in the world,
    which are expected to disappear in the foreseeable
    future due to non-native beachgrass
    stabilization (Cooper 1958; Crook 1979).
    According to a draft environmental impact
    statement by Siuslaw National Forest (1993
    as cited in Wiedemann and Pickart 1996), the
    unique open dunes will completely disappear
    by 2040, a process which can only be reversed
    by removing the foredune, a cost-prohibitive
    solution.

    Wiedemann and Pickart (1996) temper the
    threat by providing evidence for the longterm
    cyclical nature of Oregon dune stabilization
    and rejuvenation over the course of
    the past 3,000 years; a recurring process in
    which vegetation-induced dune stabilization
    creates a foredune, which is then eliminated
    during major natural disturbances (e.g., subduction zone earthquake, tsunami, sea
    level rise), releasing interior dunes once again
    to wind-driven sand movement. They suggest
    that non-native beachgrasses may only be
    hastening a natural cyclical process.

    Butterfly bush (Buddleja davidii formerly B.
    variabilis
    )

    Similar to Scotch broom (below), butterfly
    bush dominates open disturbed habitat, and is especially problematic to re-forested
    lands where it smothers tree seedlings (ODA
    2014a). Butterfly bush can grow to 12 ft (3.6
    m) in height and 15 ft (4.6 m) across and produces
    an abundance of wind-dispersed seeds
    (USFS 2005b).

    Canada thistle (Cirsium arvense))
    Canada thistle spreads aggressively through
    agricultural lands, riparian areas, wet meadows,
    and roadsides both vegetatively and
    from seed (up to 5,000 per plant)(USFS
    2006a). Control of established populations
    can be difficult because even small root segments
    can form new plants (OSU 2006).

    Cherry laurel (Prunus laurocerasus))
    Also known as English laurel, cherry laurel can
    “escape” from cultivated hedges, spreading
    into nearby forest lands. Cherry laurel is a
    shade tolerant plant that can grow to 30 ft
    (9 m) tall and is toxic (especially the seeds) if
    ingested (USDA 2010).

    Cordgrasses (Spartina spp.))
    Except where otherwise noted, the following
    information is provided by Howard et al.
    (2007). Only one Spartina species (S. foliosa)
    is native to the U.S. West Coast. Four other
    Spartina species found in the region are
    non-native and considered particularly invasive:
    Common cordgrass (S. anglica), smooth
    cordgrass (S. alterniflora), dense-flowered
    cordgrass (S. densiflora), and saltmeadow
    cordgrass (S. patens). Common cordgrass is
    a hybrid between the European cordgrass (S.
    maritima, not found on the U.S. West Coast)
    and smooth cordgrass.

    Common and smooth cordgrasses colonize West Coast estuaries,
    converting widespread unvegetated low intertidal
    mudflats to marsh habitat. These marshes
    are dominated entirely by Spartina since
    no native marsh plants are adapted to grow in
    the low intertidal zone. This dramatic habitat
    shift affects native plant and animal species
    that rely on intertidal mudflats (e.g., shore
    birds, native clams, eelgrass), and severely
    limits recreational and commercial uses of
    those same mudflats (e.g., commercial oyster
    cultivation, recreational clamming). Smooth
    cordgrass is the most aggressively spreading
    of the four species and is also able to occupy
    the broadest elevation range (mudflat to high
    marsh).

    Dense-flowered and saltmeadow
    cordgrasses are better adapted to local marsh
    habitats where they aggressively outcompete
    native salt marsh species.
    All four non-native Spartina species can
    reproduce both sexually (seeds), flowering
    late summer into early fall, and by vegetative
    means (i.e. rhizome fragments).

    Reed canary grass (Phalaris arundinacea)

    medium-high-env-threat-butterfly-icon

    Reed canary grass (Figure 13) commonly
    occurs in freshwater wetlands and on agricultural
    lands in the project area. However,
    distribution of the species and the extent of
    invasion have not been documented locally.
    Magee et al. (1999) evaluated 96 freshwater
    wetland sites in the Portland (OR) area and
    found that the most frequently found invasive
    species was reed canary grass (93% of sites).
    In a related study by Magee and Kentula
    (2005), freshwater wetlands (43 study plots in
    seasonal, perennial, and open water wetlands
    within the Portland, OR urban growth boundary)
    where reed canary grass was present
    averaged 67% cover.

    Figure 14. Discrete (small, isolated) and Gross (large, dense) infestations of purple loosestrife (Lythrum salicaria) in the project area as surveyed by Coos Watershed Association staff in 2014. Subsystems: SS = South Slough; LB = Lower Bay; UB = Upper Bay; PS = Pony Slough; IS = Isthmus Slough; CS = Catching Slough. Source: CoosWA 2014b

    Figure 14. Discrete (small, isolated) and Gross (large, dense)
    infestations of purple loosestrife (Lythrum salicaria) in the
    project area as surveyed by Coos Watershed Association
    staff in 2014. Subsystems: SS = South Slough; LB = Lower
    Bay; UB = Upper Bay; PS = Pony Slough; IS = Isthmus Slough;
    CS = Catching Slough. Source: CoosWA 2014b


    Buttercup (Ranunculus spp.)

    There are numerous native and non-native
    buttercup species in Oregon. Introduced
    buttercups include: R. arvensis, R. bulbosus,
    R. ficaria, R. sardous, R. muricatus, R. parviflorus,

    and R. repens. The latter three occur
    in Coos County (USDA 2015). Of these three,
    creeping buttercup (R. repens) is considered
    the most problematic both environmentally
    and economically (Burrill 1996).

    Tansy ragwort (Senecio jacobaea)

    Already widespread in Coos County, tansy
    ragwort thrives in cool, wet, cloudy weather,
    like that seen along the Oregon coast (OSU
    2008b).

    Biddy-biddy (Acaena novae-zelandiae)

    Biddy-biddy’s distribution is limited in Coos
    County and in the project area. It’s been reported in the lower Coos estuary near Empire
    and in the upper South Slough estuary (C.
    Cornu, pers. comm. 2015; EDDMapS 2014;
    ODA 2014a).

    Cotoneaster (Cotoneaster spp.)

    Multiple cotoneaster species have been introduced
    in Oregon including C. simonsii which
    is found in Coos County including the project
    area. Other species found elsewhere may
    pose threats in the future:C. franchetii , C.
    lacteus
    (Lane and Curry counties); C. horizontalis,
    C. divaricatus, C. nitens
    (Lane County); C.
    acuminatus
    (Benton County); and C. pannosus
    (Jackson County)(USDA 2015).





    Background

    Below are detailed descriptions of the specific
    threats posed by each of the non-native and
    invasive plant species included in this data
    summary (species listed alphabetically):

    American Beachgrass (Ammophila breviligulata):
    See “Beachgrasses” on the right.

    Armenian blackberry (Rubus armeniacus)
    (formerly Himalayan blackberry, Rubus
    discolor
    )

    According to ODA (2014a), this invasive blackberry
    is the most economically damaging
    non-native species in western Oregon due to
    control costs on public and private rights-of-way,
    agricultural pasture and crop lands, and
    timberlands. The estimated economic impact of Armenian blackberry infestations and
    associated control costs in Oregon is over $40
    million. When all susceptible acres of land are
    considered, this estimate could rise to $268
    million (ODA 2014b). Armenian blackberry,
    which severely alters native ecosystems, can
    grow 20 feet per year and reproduces with
    prolific berry production, or vegetatively by
    rooting the tip of the cane when it touches
    the ground (ODA 2014a). Commonly found
    in open riparian areas, blackberry thickets
    provide little shade for streams and prevent
    native shade-producing trees and shrubs to
    colonize stream banks.

    Biddy-biddy (Acaena novae-zelandiae)
    Biddy-biddy is a low-growing perennial forb
    (non-grass herbaceous plant) that prefers
    disturbed open sites (e.g., stablilized dunes
    or open scrub communities) and competes
    poorly with established native vegetation
    (ODA 2014a). Its seed exteriors feature
    barbed burs that cling tenaciously to almost
    anything, allowing the seeds to spread far
    and wide by mobile species including mammals,
    birds and humans. Biddy-biddy can also
    spread vegetatively by the growth of aboveground
    “stolons” (horizontal stems)(ODA
    2014a).

    Brass Buttons (Cotula coronopifilia)
    Brass buttons is a non-native, non-invasive
    species commonly found in disturbed wetlands
    and beaches in every Oregon coastal
    county. Brass buttons is easily outcompeted
    by native vegetation.

    Brazilian waterweed (Egeria densa))
    Exported from South America for use in
    aquariums, Brazilian waterweed has escaped
    to infest local lakes, ponds, and slow moving
    rivers where it forms dense mats on the
    water’s surface. Once established, Brazilian
    waterweed slows or stops water flow, traps
    sediments, displaces native aquatic species,
    and interferes with recreational activities
    (e.g., swimming, boating)(Figure 13). Interestingly, all Brazilian waterweed plants in the
    U.S. are male, but they still manage to spread
    vegetatively (WSDE n.d.).

    Bull thistle (Cirsium vulgare))
    Reaching 5 ft (1.5 m) tall and 3 ft (0.9 m) in
    diameter, bull thistle is made up of many
    spiny branches and can develop taproots
    that extend 28 inches (71 cm) into the soil
    (OSU 2008a; USFS 2005a). Seeds are wind
    dispersed and can remain viable for up to 10
    years (OSU 2008a). This thistle is most commonly
    found in disturbed areas such as along
    roadsides and in pastures in poor conditions,
    though it can also be found in cleared forestland
    (OSU 2006; USFS 2005a). Bull thistle can
    reduce agricultural productivity by forming
    large, dense stands in pastures. Bull thistle
    also grows in native plant communities,
    out-competing these plants for water, nutrients
    and space.

    Buttercup (Ranunculus spp.):) Of all the
    non-native plant species found in Coos County,
    creeping buttercup (R. repens) is the most
    invasive, spreading by stolons and forming
    thick carpets in wet meadows (Burrill 1996).
    In buttercup-infested pasture lands this plant can poison and sometimes kill livestock (Burrill
    1996). Creeping buttercup is also highly
    invasive in moist riparian terraces and wetlands,
    dominating streamside plant communities
    (NPSO 2008)

    Cotoneaster (Cotoneaster spp.)
    Cotoneaster species frequently escape garden
    plantings and are considered moderately
    invasive in coastal Oregon woodlands and
    prairies (NPSO 2008). On occasion, populations
    can become dense enough to crowd out
    native vegetation (DiTomaso et al. 2013).
    Dalmatian Toadflax (Linaria dalmatica)

    Dalmatian toadflax is a potentially serious
    weed that invades agricultural lands. It is
    resistant to many herbicides, hosts several viruses
    that can transfer to crops, outcompetes desirable forage plants while having no forage
    value itself, and is difficult to eradicate once
    established (Figure 8). Control costs are currently
    estimated at over $250,000 per year.
    If all Oregon lands susceptible to infestation
    were covered by this species, annual control
    costs could reach over $20 million (ODA
    2014b). Toadflax vegetative budding roots can
    extend up to six feet (1.8 m) deep and spread
    laterally up to 12 ft (3.6 m). Mature toadflax
    plants can produce as many as 500,000 seeds
    each year. This species commonly invades
    open disturbed areas such as roadsides and
    cultivated fields but rarely occurs in intact
    natural areas. Toadflax is not known to be
    used by local animals except as cover for
    small animals (Zouhar 2003).

    Diffuse knapweed (Centaurea diffusa)
    See ‘Knapweeds and Starthistle’ below.
    English holly (Ilex aquifolium)
    A common ornamental, English holly frequently
    escapes garden plantings and is
    considered moderately invasive in Oregon
    woodlands and prairies (NPSO 2008). English
    holly is a shade tolerant species that is
    frequently associated with increasing forest
    stand density. English holly populations in
    Oregon are expected to spread significantly in
    coming years (Gray 2005).

    English ivy (Hedera helix)
    English ivy is a perennial evergreen climbing
    vine that covers trees to canopy height,
    sometimes creating enough biomass that its
    weight topples trees. English ivy also spreads
    horizontally along the forest floor, displacing
    all native vegetation in its path (ODA 2014a).
    It is considered a threat to native plant communities
    in Oregon and has been placed on
    ODA’s 2010 list of quarantine species (Waggy
    2010). English ivy has a high tolerance to
    varying light conditions, thriving in both full
    shade and full sun. It can survive in early to
    late successional forests (Waggy 2010).

    Eurasian watermilfoil (Myriophyllum spicatum)
    See ‘Watermilfoil’ below.

    European Beachgrass (Ammophila arenaria)
    See “Beachgrasses” above.

    False Brome (Brachypodium sylvaticum)
    Brought to Oregon in the late 1930’s by USDA
    as one of several grasses for range enhancement
    experiments, false brome has since
    escaped into Oregon’s landscape (Figure 8).
    False brome is a perennial grass that thrives
    in both shady and sunny conditions, creating
    thick monoculture (single-species) mats that
    can outcompete native herbaceous vegetation
    and prevent native tree species’ seeds
    from germinating. Further, false brome does
    not provide good forage, reducing pasture
    productivity (Davi 2009).

    Field bindweed (morning glory)(Convolvulus
    arvensis
    )

    Competing with crops for nutrients and
    water and extremely difficult to remove, field
    bindweed can reduce crop yields by as much
    as 50% (ODA 2014a). One plant can produce
    up to 500 seeds, which remain viable in the
    soil for up to 20 years (USFS 2006b). This climbing vine has lateral roots that can sprout
    new plants from small root or vine fragments,
    greatly complicating eradication measures
    (USFS 2006b; Zouhar 2004a).

    French Broom (Genista monspessulana)
    An aggressive pioneer species that displaces
    native early colonizing plants in disturbed
    areas, French broom can drive up invasive
    species control costs in timber harvest areas
    and create a severe fire hazard during the dry
    season (Figure 13)(ODA 2014a). A medium
    sized French broom shrub can produce over
    8,000 seeds per year, which are explosively
    ejected by the pod up to 13 ft (4 m) from the
    parent shrub (Bossard 2000, Zouhar 2005b).
    Over half the seeds from these dense woody
    shrubs are dormant upon dispersal. Germination
    takes place only under specific environmental
    conditions (e.g., scarification of the
    seed shell); seeds remain viable in the soil
    for up to 5 years (Adams et al. 1991, Bossard
    2000b).

    Garlic Mustard (Alliaria petiolata)
    Extremely difficult to control once established,
    garlic mustard thrives in partial shade
    and forms dense thickets in forest understories,
    displacing native species (Figure 3). It
    can also infest riparian zones, roadsides, trails
    and agricultural lands and is almost totally
    reliant on seed production to spread (ODA
    2014a). Garlic mustard can grow as tall as 3.5
    feet (1 m)(USFS 2005c) and does not tolerate
    acidic soil, likely explaining its absence from
    conifer-dominated communities. This invader
    appears to negative affect native butterfly
    populations by fatally inhibiting larval development
    in butterfly eggs deposited on its
    leaves (Munger 2001).

    Giant Hogweed (Heracleum mantegazzianum)
    Unlike its native relative, cow parsnip (H.
    maximum), giant hogweed adversely affects
    both local economies and native plant communities
    (ODA 2014a). Most common in partial
    shade or full sun, giant hogweed readily
    invades riparian areas where it outcompetes
    native species, provides poor winter groundcover
    for animals, and leads to increased
    bank erosion during winter rains (Thiele and
    Otte 2006, DiTomaso and Healy 2007, Forney
    2013). Forney (2013) describes giant hogweed
    as a human health hazard, since its sap
    contains a chemical that can cause severe
    burns on UV exposed skin, prompting the
    need for targeted control programs in public spaces. Although this plant is currently only
    found in very limited areas in Oregon, potential
    economic impact to the state (in lost
    agricultural production and control costs) if it
    was to infest all susceptible habitat would be
    over $1 million per year (ODA 2014b).

    Giant hogweed is a large plant, growing
    approximately 15 ft (4.5 m) tall with flower
    heads and leaves that can be 3 ft (0.9 m) or
    more in diameter (ODA 2014a). It grows from
    a single hollow stem that can be 6 inches (15
    cm) in diameter (Figure 5)(Page et al. 2006).
    Seeds can float in water for two days and remain
    viable, allowing this plant spread via waterways
    (Gucker 2009). Because of its size and
    prolific seeding ability (each flower head can
    produce 1,500 seeds), giant hogweed easily outcompetes native species (USFS 2005d).
    According to Gucker (2009), giant hogweed
    seeds are capable of germinating within the
    first year of dispersal; the plants generally
    flower in three years and then die.

    Figure 15. Continuous coverage of invasive Japanese eelgrass (Z. japonica) in Willipa Bay, WA at a site that was unvegetated mudflat 10 years prior. Source: Fisher et al. 2011

    Figure 15. Continuous coverage of invasive Japanese eelgrass(Z. japonica) in Willipa Bay, WA at a site that was unvegetated mudflat 10 years prior. Source: Fisher et al. 2011


    Reed canary grass (Phalaris arundinacea))
    There is some confusion as to the native status
    of this perennial grass. It’s likely native to
    parts of North America, but has been cultivated
    for livestock fodder with non-native strains
    and is now considered an invasive plant that
    is a major threat to natural freshwater wetlands
    (Figure 13)(Apfelbaum and Sams 1987,
    Lavergne and Molofsky 2007).

    An aggressive invader, reed canary grass quickly spreads both vegetatively (by creeping
    rhizomes (i.e., rootstock)) and by seed
    (individual seed heads can produce up to
    600 seeds). Reed canary grass seeds can
    germinate immediately after dropping with
    no dormancy requirements (Apfelbaum and
    Sams 1987, Tu 2004).

    Associated with a reduction in native plant
    species richness, reed canary grass often
    approaches 75-100% cover in the areas is invades
    (Houlahan and Findlay 2004, Mulhouse
    and Galatowitsch 2003). As an example, an
    Oregon study by Schooler et al. (2006) found
    that native species abundance declined exponentially with increasing cover of reed canary
    grass. Likewise, along the Willamette River in
    Oregon, Fierke and Kauffman (2006) found
    that reed canary grass abundance was negatively
    correlated with species richness and
    understory species diversity in established
    riparian forest stands.

    Perkins and Wilson (2005), found a strong negative correlation between native plant
    community diversity in beaver-dammed wetlands along the Oregon coast and reed
    canary grass infestations. They suggest that
    the cyclical nature of disturbance associated
    with beaver dam abandonment/beaver pond
    draining provides ideal opportunities for reed
    canary grass invasions, chronically suppressing
    natural wetland communities.

    Animals are also adversely affected by reed
    canary grass. In a study by Spyreas et al.
    (2010), wetland plant diversity and abundance of Homoptera insects (true bugs such
    as shield bugs and leafhoppers) decreased as
    reed canary grass populations increased.
    Reed canary grass is extremely difficult to
    completely eradicate once established. Mechanically
    removed red canary grass stands
    quickly grow back from seed stocks and rhizomes
    remaining in the soil. Apfelbaum and
    Sims (1987) describe how reed canary grass
    continued to persist even as test plots were clipped to ground level and covered with
    black plastic for two growing seasons. However,
    since this species requires full sunlight,
    Kim et al. (2006) found that reed canary grass
    populations decreased 68% within two years
    by being shaded by willow plantings.

    Scotch broom (Cytisus scoparius))
    Scotch broom is a perennial shrub that can
    grow to 8 ft (2.5 m) tall in almost any soil
    type. It is considered the worst nuisance
    plant on Oregon forest lands, substantially
    increasing costs associated with timber land
    re-forestation (Figure 13). Once established,
    scotch broom is difficult to control, costing
    an estimated $47 million dollars annually in
    lost timber production and control costs (ODA 2014a). In Oregon and Washington, complete
    stand failure of Douglas-fir plantings has occurred
    due to Scotch broom infestations (Peterson
    and Prasad 1998). Scotch broom also
    displaces native colonizing species in multiple
    habitat types (e.g., forestlands or dunes), in
    both disturbed and undisturbed areas (ODA
    2014a).

    Scotch broom spreads by seed. Typically, a
    handful of seeds are projected from its seed
    pods, dispersing an average of 3 ft (0.9 m)
    from the parent plant (Zouhar 2003). Bossard
    (2000a) estimates seeds can remain viable
    in the soil for 30 years. They add that nearly
    100% of seeds are viable but dormant when
    released from the pod, requiring scarification
    (damage to the seed coat) in order to allow water to penetrate and the seed to germinate.
    The environmental conditions required
    to release dormancy are not yet understood.
    Along with seed production, brooms can
    sprout from root stumps following damage
    (e.g., from mowing or fire)(Zouhar 2005a).

    Slender flowered thistle (Carduus tenuiflorus))
    Slender flowered thistle can grow to 6 ft (1.8
    m) tall, invade disturbed areas (e.g., vacant
    lots, old fields) and reduce forage productivity
    of less healthy pastures. However, it rarely
    overtakes healthy grasslands or native vegetation
    (DiTomaso and Healy 2007). Plants can
    produce as many as 20,000 seeds annually,
    which can remain dormant but viable in the
    soil for up to 10 years (Marriott et al. 2013).

    Spanish Heath (Erica lusitanica))
    Spanish heath is extremely prolific, able to
    produce nine million seeds per plant. It can
    create thick single-species stands in disturbed
    areas, potentially affecting Coos County
    timber and pasture lands (Figure 8). Since
    mowing has no lasting effect on controlling
    Spanish heath (plants do not die, just re-vegetate
    horizontally, creating dense mats), costly
    herbicide applications are expected to be the
    only method available for effectively controlling
    this invasive species (French 2009).

    Spiny cocklebur (Xanthium spinosum))
    Found in a variety of disturbed habitats,
    ingestion of Spiny cocklebur seedlings can be
    fatally toxic to livestock. Spiny burs can cling to animals and humans or float on water in
    order to disperse (DiTomaso et al. 2013).

    Spotted Knapweed (Centaurea stoebe formerly
    C. maculosa)

    See ‘Knapweeds and Starthistle’ above.

    Spurge (Euphorbia spp.))
    Both oblong and leafy spurges (E. oblongata
    and E. esula) are highly toxic to livestock and
    irritating to human skin and eyes. The spurges’
    milky sap contains the toxin ingenolis (St.
    John and Tilley 2014). Ingenolis is potent
    enough to cause blistering and hair loss
    around horses’ hooves put in recently mowed
    pastures infested with leafy spurge (Gucker
    2010). Leafy spurge’s massive root system can vegetatively reproduce (even when pieces are very
    small, partially dried and deeply buried), and can extent to nearly 15 ft (4.5 m) deep (Gucker
    2010). This, along with its highly prolific
    seeding capability and its ability to establish
    itself in both disturbed and undisturbed sites
    in a variety of habitats, allows leafy spurge
    to successfully outcompete native vegetation
    (Gucker 2010, St. John and Tilley 2014).

    Once established, leafy spurge is very difficult
    to eradicate. In fact, the Canadian Botanical
    Association ranked leafy spurge as 6th of 81
    invasive species seriously affecting natural
    habitats in Canada (St. John and Tilley 2014,
    Catling and Mitrow 2005 as cited in Gucker
    2010). Cattle will not graze in areas where leafy spurge is 10% cover or greater, degrading
    pasture carrying capacity by 50-75%. Leafy
    spurge currently costs the state an estimated
    $17,000 per year to control, but has only just
    gained a foothold (0.2% of likely habitats are
    currently infested). If it spread to its maximum
    potential, leafy spurge control measures
    could cost the state over $65 million per year
    (ODA 2014b). Well adapted to a wide variety of habitats, in western Oregon, oblong spurge thrives in
    moist grassy bottomlands (including pastures)
    and sunny riparian areas, out-competing native
    vegetation. Oblong spurge is also a showy
    perennial herb cultivated commercially as an
    ornamental plant (ODA 2014a).

    St. John’s wort (Hypericum perforatum))
    St. John’s wort is commonly found growing on disturbed lands (e.g., roadsides, agricultural
    sites). Once established, St. John’s wort will
    decrease forage productivity in pasture lands and poison livestock with a photosynthesizing
    chemical (hypericin) that causes blisters,
    blindness or swelling of the animal’s mouth,
    preventing them from grazing or drinking
    (Crompton et al. 1988, Zouhar 2004b). St.
    John’s wort is a prolific seeder (up to 34,000
    seeds per plant)(Crompton et al. 1988). However,
    seedlings are slow growing, especially
    during summer drought conditions, making
    them susceptible to competition from other
    plant species (Tisdale et al. 1959, Campbell
    1985).

    Perhaps this plant’s most problematic effects
    are loss of grazing capacity in pastures where
    it takes over. Sampson and Parker (1930)
    reported that St. John’s wort shades out desirable
    pasture vegetation and removes large
    quantities of moisture from the soil. Seedling
    survival of St John’s wort for most years is
    extremely low, because the plant is unable to tolerate summer drought conditions. However,
    due to the sizable and persistent seed
    banks associated with St. John’s wort infestations,
    this plant’s populations can remain
    dormant for many years, only to expand rapidly
    through seed germination to cover large
    areas during wetter years.

    Sweet Fennel (Foeniculum vulgare))
    Sweet fennel is a perennial that invades open
    disturbed areas like roadsides and coastal
    scrub land, sometimes developing into dense
    stands that can displace native flora. It can
    grow to 10 ft (3 m) tall (DiTomaso et al. 2013).

    Tansy Ragwort (Senecio jacobaea))
    Tansy Ragwort is a poisonous member of the sunflower family. All parts of tansy ragwort
    are poisonous, causing lethal liver damage
    to most livestock if consumed. Normally
    biennial (lives 2 years), mowed or damaged
    plants will continue to regrow until seeds are
    produced. A prolific seed producer (200,000
    seeds per plant), tansy ragwort seeds can last
    15 years in the soil and still remain viable.
    Tansy ragwort is able to grow 6 ft (1.8 m) tall
    with a taproot that penetrates the soil up to 1
    ft (0.3 m) deep, and requires open, disturbed
    habitat to become established (OSU 2008b).
    Prior to an extremely successful biological
    control program begun in the 1960’s using the
    cinnabar moth, tansy ragwort flea beetle, and
    a seed head fly, Oregon lost over $5 million
    per year in control and lost productivity costs.
    Since then, cattle losses from tansy ragwort
    poisoning have become rare and lost productivity
    costs have decreased to an estimated
    $115,000 per year (ODA 2014b). It should
    be noted, however, that changing climate
    conditions may favor tansy ragwort growth
    while limiting productivity of the beneficial
    insects used to control the plant, thus helping
    tansy ragwort populations rise once again in
    western Oregon (OSU 2011).

    Velvetleaf (Abutilon theophrasti))
    Generally only invasive in very disturbed
    areas, velvetleaf has become a serious threat
    to orchard and croplands (USFS 2006e). Seeds
    from this species can lie dormant in soil for
    over 50 years (USFS 2006e).

    Watermilfoil (Myriophyllum spp.))
    Eurasian watermilfoil (M. spicatum) and Parrot’s
    feather (M. aquaticum) are two freshwater aquatic plants that colonize slow moving
    water (e.g., lakes, ponds), forming dense
    mats on the water’s surface (Figure 12). Both
    species can thrive in eutrophic (excessive
    nutrient) conditions. Parrot’s feather can grow up to a foot above the surface of the water, resembling small fir trees, while Eurasian watermilfoil forms long
    (up to 5 ft [1.5 m]) intertwining stems that
    grow near the water’s surface. Infestation of
    either species reduces fish production and native
    plant diversity, helps increase mosquito
    populations, and is a general nuisance for recreational users (e.g., swimmers and boaters)
    (ODA 2014a).

    Woolly Distaff Thistle (Carthamus lanatus))
    An especially significant nuisance in pasture lands, woolly distaff thistle can grow to 4 ft
    (1.2 m) tall and remain rigid and upright even
    after it dies, creating a formidable barrier to
    grazing livestock (OSU 2006). French (2010)
    notes that dense infestations can also clog
    harvesting equipment. Woolly distaff thistle
    seeds remain viable for up to 10 years, creating
    the need for aggressive control measures
    in established populations and prevention
    strategies on susceptible lands to maintain
    productive grazing lands (French 2010).
    In the 1980s, the ODA Weed Program successfully
    implemented a woolly distaff thistle
    prevention campaign, which has kept the
    wooly distaff thistle infestation to less than
    four acres in Oregon. This success translates
    to an estimated economic impact of less than
    $500 per year. In the absence of the sustained state-wide early-detection program, woolly
    distaff thistle control measures are estimated
    to cost over $164 million per year (ODA
    2014b).

    Yellow Flag Iris (Iris pseudacorus))
    Yellow flag iris is an aquatic plant that can
    thrive in a wide range of environmental
    conditions (e.g., fresh to brackish waters, wetlands,
    rocky shores, stream banks or ditches)
    and can form dense impenetrable thickets
    that displace native vegetation and alter
    habitat for animals (Figure 8)(USFS 2006c). Its
    buoyant seeds allow widespread dispersal by
    water. Yellow flag iris can also propagate vegetatively by rhizome (i.e., rootstock), creating
    laterally spreading clones that displace native
    aquatic vegetation (Stone 2009; USFS 2006c).

    Yellow Glandweed (Parentucellia viscosa))
    This annual hemiparasite (obtains some nutrients
    from a host plant) invades coastal wetland
    prairies and pastures, thriving especially
    in dune wetlands (Pickart and Wear 2000). A
    1996 study in Humboldt Bay dunes habitat
    by Pickart and Wear (2000) found that yellow
    glandweed is a prolific seeder (12,000 seeds per plant) allowing an extensive seed bank
    to build in underlying soils. However, native
    plant species did not appear to be affected by
    the presence of yellow glandweed, suggesting
    that this non-native plant is not particularly
    invasive.

    Yellow Starthistle (Centaurea solstitialis))
    See ‘Knapweeds and Starthistle’ above.

    Gorse (Ulex europaeus)
    Gorse is considered one of the most unmanageable
    weeds in the world, significantly
    affecting both native habitats and local economies
    (e.g., managed forestland) by forming
    impenetrable thickets that persist and thrive
    for many years (Figure 12)(ODA 2014a). A
    perennial, densely spiny shrub that can live
    for over 40 years, gorse colonization results
    in the development of large seed banks in
    underlying soils, which severely complicate
    eradication efforts.

    Gorse seeds, which can remain dormant but viable for up to 30 years,
    require scarification (damage to outer seed
    case) in order to germinate (Zouhar 2005c).
    Gorse currently infests less than 0.2% of possible
    area it could inhabit in Oregon but still
    costs the state an estimated $441,000 in lost
    economic activity and control measures. If it
    were to cover all susceptible lands, it would
    cost over $205 million to control.

    Herb Robert (Geranium robertianum)
    Herb Robert can affect native flora, with localized
    densities of 250 plants/m2. Herb Robert’s
    roots, however, are shallow, allowing for easy
    manual control. According to ODA (2014a),
    herb Robert can invade open forest or forest
    edge habitat, and can also thrive in shady
    conditions, allowing it to directly compete
    with native understory plant communities
    (Figure 7).

    Japanese eelgrass (Zostera japonica)
    The invasive status of Japanese eelgrass is
    debated. Evidence supports both its potential
    benefits and harmful effects. The following
    describes Japanese eelgrass’s positive, negative
    and neutral effects on the local ecosystem.

    Positive: Waterfowl (e.g., mallards) prefer
    grazing on Japanese eelgrass over native eelgrass,
    possibly due to the higher caloric value
    and easier foraging accessibility of the former
    (Baldwin and Lovvorn 1994).
    According to Ferraro and Cole (2012), benthic
    macroinvertebrates species richness, abundance,
    and biomass are greater in Japanese
    eelgrass beds compared with native eelgrass
    beds.

    Posey (1988) demonstrated that species
    diversity was higher in Japanese eelgrass
    beds than in adjacent unvegetated areas in
    the South Slough. Supporting Posey’s results,
    Javier (1987), also studying Japanese eelgrass habitats in the South Slough, found
    that the four most common spionids (worm
    species considered prey resources for various
    animals) were found in significantly higher
    densities in Japanese eelgrass beds compared
    to surrounding mudflats. This result supports
    the theory that Japanese eelgrass provides
    refuge for prey resources.

    Negative: Able to spread through both seed
    production and vegetatively, Japanese eelgrass
    roots create a dense sodlike matrix, able
    to completely cover substrate surfaces (Fisher
    et al. 2011, Posey 1988).

    In Willapa Bay, WA, Japanese eelgrass populations
    remained relatively confined for
    50 years after introduction until 1998 when
    they began to greatly expand (likely surpassing
    some critical population/reproductive
    threshold), covering large swaths of formerly
    unvegetated estuarine mudflat (Figure 14).
    Japanese eelgrass then began to outcompete
    native eelgrass (in the transition zone where
    the two species overlap) and spread into
    existing low salt marsh habitat (Fisher et al.
    2011). Coverage of unvegetated mudflats by
    Japanese eelgrass and its heavily matted root
    structures may also adversely affect burrowing
    benthic macroinvertebrates that colonize
    open mud habitats (Posey 1988).

    Rumrill and Kerns (1991) found that juvenile
    Dungeness crabs (Cancer magister) accidentally
    settle in Japanese eelgrass beds, at higher
    intertidal elevations than they normally
    would, leaving the young crabs more susceptible
    to predators and desiccation.

    Neutral: Known to overlap with native eelgrass
    (Z. marina) in other estuaries, Japanese
    eelgrass in the Coos estuary thus far colonizes
    discretely higher intertidal elevations (Dudoit
    2006). Fisher et al. (2011) explain that native
    eelgrass can often suppress the density of
    Japanese eelgrass in beds where the species
    co-occur. However, a critical Japanese eelgrass
    population threshold may not yet have
    been reached in the Coos estuary (see Willipa
    Bay example in the Japanese eelgrass “Negative”
    section above).

    Like the native eelgrass, Japanese eelgrass
    traps and stabilizes sediments and slows tidal
    currents to the benefit of smaller fish and
    crustaceans. Its senesced leaves contribute to
    the estuary’s detrital food web, and it radically
    changes the character of formerly unvegetated
    mudflats. Long-term Japanese eelgrass
    colonization can result in significantly smaller
    mean sediment grain size, significantly higher
    levels of volatile organics (an indicator of detritus),
    and higher benthic macroinvertebrate
    density and species richness compared with
    adjacent unvegetated mudflats (Posey 1988).
    Finally, in Oregon, Pacific herring use both
    Japanese eelgrass and the native eelgrass as
    spawning substrate (Matteson 2004).

    Jubata grass (Cortaderia jubata)
    Frequently confused with the related invasive
    pampas grass (C. selloana), the perennial
    jubata grass can grow to 7 m (23 ft) tall. A
    single plant can grow roots that spread 3.5
    m (11 ft) deep and 4 m (13 ft) wide, easily crowding out native vegetation (especially in
    native grasslands) and out-competing seedling
    trees in timber managed areas (Figure 13)
    (ODA 2014a; Marriott et al. 2013).

    Damaging even in small populations because of its rapid
    growth and formidable size, the large clumping
    grass once established can be very difficult
    to remove (Peterson and Russo 1988). Jubata
    grass is a prolific seeder (millions of seeds per
    plant) that does not require pollination. These
    giant grass plants can spread quickly because
    their numerous seeds are light and can travel
    easily on the wind (Peterson and Russo 1988).

    Knapweed or starthistle (Centaurea spp.))
    Diffuse knapweed (C. diffusa) is a highly prolific
    plant (18,000 seeds per plant) that forms
    dense thickets in a wide range of conditions,
    including gravel banks, sandy riparian areas,
    rock outcrops, and agricultural pasture lands.
    (Figure 5). Health hazards associated with this
    species include skin irritation due to plant
    juices and bites from associated mites (ODA
    2014a, 2014b). It is an extremely difficult
    plant to manage once established.

    The expense associated with controlling and eradicating
    diffuse knapweed can often exceed
    the income potential of the pasture or forage
    lands it invades (Beck 2013, USFS 2014, Zouhar
    2001a).

    Meadow knapweed (C. pratensis)) is a hybrid
    of brown knapweed (C. jacea) and black or
    common knapweed (C. nigra). According
    to ODA (2014a), this invader prefers moist
    open conditions such as wet pastures and
    riverbanks where it frequently outcompetes
    native and forage grasses, causing declines in pasture productivity. They add that once
    established, this plant is difficult to eradicate.
    Hand-pulling is a challenge due to the plant’s
    woody root crown, and long-term herbicide
    regimens are only effective if maintained for
    many years.

    Meadow knapweed’s current annual economic
    impact to the State of Oregon is estimated
    at $146,000. However, at present it only covers
    1% of possible habitats. If it were to infest
    all potential habitats, it could cost the state
    over $15 million per year (ODA 2014b).
    Spotted knapweed (C. stoebe formerly C.
    maculosa), one of the most dominant weeds
    in the western US, spreads primarily by seed
    but can also spread vegetatively by sprouting
    lateral shoots (Beck 2013; Zouhar 2001b).

    This species releases a toxin into the soil that
    hinders growth of neighboring vegetation,
    reducing competition from native species
    (USFS 2006d). Considered a serious threat
    to Oregon rangelands, this perennial plant
    is able to live nine years (Zouhar 2001b).
    Spotted knapweed’s estimated economic
    impact to Oregon thus far is limited ($33,000)
    but could grow. Luckily for Oregon’s coastal
    communities, however, habitat suitability for
    spotted knapweed west of the coast range is
    scarce (ODA 2014b).

    Yellow starthistle (C. solstitialis)) is a prolific
    seed producer, thrives in full sunlight in areas
    of summer drought, and can grow 3-6 ft (0.9-
    1.8 m) tall (OSU 2008c). A single plant is able
    to produce 150,000 seeds (OSU 2006) which
    can remain viable in the soil for 10 years (Callihan et al. 1993). According to Zouhar
    (2002), yellow starthistle taproots can grow
    deep enough (more than 3 ft) so that heavy
    infestations can lower the local soil water table
    below the root zone of most native plants,
    adversely affecting those plant communities.

    Yellow starthistle can cause livestock injury
    (chewing disease) especially in horses. Currently
    this plant costs Oregon an estimated
    $775,000 per year to control. Costs could
    reach nearly $28 million if this species covered
    all possible lands in Oregon with suitable
    habitat (ODA 2014b).

    Knotweeds (Polygonum spp.))
    There are four knotweeds known in the project
    area: Himalayan (P. polystachyum), giant
    (P. sachalinense), Japanese (P. cuspidatum)
    and Bohemian (P. bohemica), which is a hybrid
    between giant and Japanese knotweeds
    (Figure 12). Knotweeds form dense thickets
    along water edges, outcompeting native
    riparian species (ODA 2014a).

    According to ODA (2014a), knotweeds can grow new plants
    vegetatively from any part of the plant, above
    or below ground, making proper disposal of
    cuttings imperative for preventing its spread.
    Once established, knotweeds are extremely
    costly and time consuming to control, much
    less eradicate. Giant, Japanese and Bohemian
    knotweeds all produce extensive rooted mats
    that hinder any kind of growth from other
    plant species (Steiger 1957, Weber 1987,
    Lema 2007).

    Giant knotweed is the largest of the knotweeds,
    growing to 13 ft (4 m) tall, with 1 ft (0.3 m) long leaves, and able to spread via rhizomes
    (i.e., rootstock) up to 65 ft (20 m) laterally
    (ODA 2014a). Slightly smaller, Japanese
    knotweed grows up to 10 ft (3 m) tall with
    6 inch (15 cm) long leaves and can tolerate
    adverse conditions such as high temperature,
    salinity, drought, or full shade (USFS 2004).
    Himalayan knotweed, the least shade tolerant
    species, is even smaller growing to 6 ft (1.8
    m) tall and has narrow leaves 4-8 inches (10-
    20 cm) long (ODA 2014a).

    Meadow knapweed (Centaurea pratensis))
    See ‘Knapweeds and Starthistle’ above.

    Milk thistle (Silybum marianum))
    A large thistle, milk thistle can grow 10 ft
    (3 m) tall and 5 ft (1.5 m) in diameter (OSU
    2006). Since it can grow so large and spread
    so rapidly, OSU (2006) notes that livestock
    can be entirely displaced in pastures that are
    heavily infested with milk thistle.

    Old Man’s Beard (Clematis vitalba))

    Similar to English ivy, old man’s beard is a
    woody climbing vine that can grow up to 100
    ft (30 m) long, and can blanket entire trees or
    smother native ground cover (Figure 8). Individual
    plants can produce over 100,000 seeds
    per year, which are then easily transported by wind, water or animal. Further enhancing
    its ability to spread, small vine sections can
    regenerate into entirely new plants (ODA
    2014a).

    Parrot’s feather (Myriophyllum aquaticum))
    See ‘Watermilfoil’ below

    Pennyroyal (Mentha pulegium))
    Pennyroyal, member of the mint family, occurs
    in most coastal Oregon counties (Cal-IPC
    n.d.). Thought to be widespread and invasive
    in some Oregon freshwater wetlands, it is
    difficult to control once established (NPSO
    2008). Found primarily in seasonally flooded,
    disturbed sites (e.g. pastures or riparian
    areas), pennyroyal’s capacity to displace
    native plants is uncertain, but it is considered
    a problem species for ranchers since it can
    poison livestock (Cal-IPC n.d.).

    Poison hemlock (Conium maculatum))
    A member of the carrot family, poison hemlock
    is an extremely poisonous plant that
    inhabits pastures and irrigation ditches, growing
    3-7 ft (0.9-2.1 m) tall (ODA 2014a).

    Policeman’s Helmet (Impatiens glandulifera))
    Policeman’s helmet can form dense stands in
    moist open areas (e.g., riparian zones)(Figure
    8)(ODA 2014a). Individual plants can release
    up to 800 seeds per seed capsule, which explode
    when mature; in riparian areas, seeds
    are then easily transported downstream (ODA
    2014a).

    Portuguese Broom (Cytisus striatus))
    Portugese broom outcompetes native scrub/
    shrub vegetation (particularly in commercial
    timberland) and provides no food for native
    wildlife. Individuals can reach sizes of 20 ft (6
    m) in width, with trunk diameters of 14 inches
    (35.5 cm). Easy to confuse with the much
    more common Scotch broom, Portuguese
    broom seed pods are covered in thick white
    hair, similar to willow buds (ODA 2014a). See “Scotch Broom” below for more information
    on broom species.

    Purple loosestrife (Lythrum salicaria))
    Purple loosestrife is a perennial plant that
    spreads vegetatively by rhizomes (i.e., rootstock),
    or with seeds that disperse in water
    (Figure 13). This highly invasive freshwater
    wetland plant quickly colonizes disturbed areas
    and can create dense single-species thickets
    in wetlands and riparian edges, adversely
    affecting habitat availability for waterfowl and
    songbirds (Munger 2002, ODA 2014a).

    A prolific seeder, Purple loosestrife seed
    capsules burst at maturity projecting two to
    three million seeds per year per plant that
    disperse by water or wind and can remain
    viable for up to three years (Munger 2002,
    USFS 2005e). Rhizome spread is about a foot
    per year and long-established plants can be
    shrubby, growing up to 10 ft (3 m) tall and 5 ft
    (1.5 m) wide (USFS 2005e, Munger 2002).

    Purple loosestrife currently costs the state
    an estimated $12,000 to control. Luckily, this
    wetland invader is unlikely to reach its full
    biological potential in Oregon due to successful
    (achieves 50-95% reduction in established
    populations) and approved biological control measures (ODA 2014b).

    Locally, CoosWA has since 1999 released
    over 41,000 biological control agents (two
    beetle species and two weevil species) at 23
    of 70 purple loosestrife-infested sites in the
    project area. The release sites ranged in size
    from 0.5 to over 5 acres, large enough to support viable beetle and weevil populations
    for effective purple loosestrife control. Each
    biological control release consists of 500-1000
    beetle or weevil species which the USDA and
    ODA carefully selected over many years to
    ensure they only attack purple loosestrife (A.
    Brickner, pers. comm. 2015).

    CoosWA partners with ODA and USDA Animal
    and Plant Health Inspection Service to obtain
    the beetles and weevils, which attack many
    parts of the plant including leaves, buds,
    roots, and seeds. The insects are released in
    the late summer and monitored by CoosWA
    staff each season for effectiveness. Several
    releases and many years may be required
    before results are evident but the beetles
    and weevils have proven to be effective for
    controlling and sometimes eradicating purple loosestrife locally and throughout the country.

    So far, these insects have helped CoosWA
    staff nearly eradicate purple loosestrife from
    a two-acre site. At Coos WA’s other release
    sites, the insects have controlled purple
    loosestrife populations to varying degrees;
    the insects’ effectiveness is oftentimes influenced
    by the presence of tidal flooding at the
    site (A. Brickner, pers. comm. 2015).

    Redtop grass (Agrostis gigantean))
    This non-native perennial grass has been
    widely introduced as pasture grass and
    thrives in meadows and grasslands, but also
    frequently occurs in open riparian areas
    (Carey 1995). Red top grass is common and
    can create single species patches but is not
    considered an invasive grass (Huang and del
    Moral 1988).


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